I am new in reactjs and learning bit and pieces. I am facing an issue. The scenario is like. I have a functional component as a parent. It has a child component as a class component. I would like to set or reset the child component's state on parent's button click. Or is there any way to call the child component's any method from the parent component. I tried as
// this call from a functional component.
<PhotoPreviewUploaend setSelectedFile={setSelectedFile} ref={setImagePreviewUrl} />
Later after a button click does this:-
setImagePreviewUrl('');
I read ref attribute allows access to the component. I tried this ref between 2 class component both parent and child is class components and it works as expected. But when did the same from a functional component it has no effect at all. How can I do it?
You are not embracing react one-way data flow by using refs like that; it might not behave the way you expect;
You should pass parent state handler logic function to the child component,
then child component call it with proper value; as the result your parent state will be updated and you have nice and clean one way data flow; you can use this in any kind of component, since you don't mess with this bindings in functional components;
This example demonstrates it in action:
function App() {
// Define your state
const [someState, setSomeState] = useState(0);
return (
<div className="container">
<Child parentCallback={setSomeState} />
</div>
);
}
class Child extends Component {
render(){
return(
<div>
<button
onClick={() => this.props.parentCallback(/*someValue*/)}
>
click me!
</button>
</div>
)
}
}
Related
I have a parent component that has a button, when clicked, opens a new component inside a React.CreatePortal control.
On that CreatePortal component, I have a button like this:
return (
ReactDOM.createPortal(
<div id="portal_Game">
<div><button onClick={jump}> JUMP </button></div>
But the 'jump' function is on the parent control.
In the portal, it's not recognized.
Is there a way to fire the 'jump' on the parent from the portal?
Thanks!
Pass the jump function as a prop to the child component like this:
In the parent component pass the jump function:
...
<Child jump={jump} />
...
You can use the function in the child component via props:
...
<button onClick={props.jump}> JUMP </button>
...
I'm very very new with React. Actually I started to learn today.
I want to build a single sidebar component in a website.
I toggle a sidebar using UseState and a function called openHandler that verifies of the sidebar is already active.
I'm wondering how should I approach the toggle inside of the sidebar. How should I change the state of the sidebar if all the handle is done in the main file (App.js)
I'm really sorry if this question don't make sense.
Here is a SandBox example of what I'm talking about.
https://codesandbox.io/s/hopeful-framework-c4k1h
If someone know what should I learn to play with that would be great.
Thanks in advance
you can pass the main handler to sidebar via props and bind it to insider toggle.
appjs
...
<CartBox openHandler= {openHandler} className={ToggleCartState} />
...
cartBox.js
...
<Toggle click={props.openHandler} />
...
Nice to read https://reactjs.org/docs/lifting-state-up.html
I assume you want to be able to change the state of the sidebar by clicking a button from another sibling / child of a sibling component.
if that's the case you'll need to put the useState hook in the higher level parent, then pass the state / an it's setter method as a prop to the children that will use it.
here is an example of what I mean.
Parent Component
function parent() {
// the sidebar state
const [sidebar, setSidebar] = useState(false);
// helper function that toggles state
function toggle() {
setSidebar(!sidebar);
}
return (
<section className="Parent">
{ /* Conditional Render */
sidebar ?
<Navbar stateManager={{toggle}} />
: <HamburgerIcon stateManager={{toggle}} />
}
</section>
)
Navbar / HumburgerIcon
function Navbar({stateManager}) {
// you now passed state and it's set method to the child
const {toggle} = stateManager;
return (
<div onClick={toggle}>
component content
</div>
}
You can put them all in same file and still do the same thing.
I have a react component which uses a 3rd party library Component as a Child node. The Grand children (or the children of the 3rd party libary) are under my control. When my component receives new props it re-renders, however the 3rd party component seems to stop my components grand-children from re-rendering also, even though the props my component received, are passed to the non-re-rendering components directly
If I remove the 3rd party component then my component re-renders as do the grand-children.
render() {
<div>
<ThirdPartyComponent props={blah}>
{this.props.products.map(prod => <MyGrandChildrenComponents product={prod} />
</ThirdPartyComponent>
</div>
}
A concrete example can be found on this code sandbox: codesandbox.io/s/silly-grass-7frlx
I'd expect my MyGrandChildrenComponents component to get updated when this.props.products changes... Any hints?
This can happen if ThirdPartyComponent is a stateful component and is not handling its prop updates correctly. One way to force a re-render is to add a key prop to your ThirdPartyComponent and update its value when a re-render is needed.
render() {
<div>
<ThirdPartyComponent key={something-that-changes-when-rerender-needed} props={blah}>
{this.props.products.map(prod => <MyGrandChildrenComponents product={prod} />
</ThirdPartyComponent>
</div>
}
If ThirdPartyComponent is a PureComponent it should re render (and so re render its children) when one of its props changes so you can try:
render() {
<div>
<ThirdPartyComponent props={blah} products={this.props.products}>
{this.props.products.map(prod => <MyGrandChildrenComponents product={prod} />
</ThirdPartyComponent>
</div>
}
To trigger re renders when this.props.products changes.
But any prop should do.
If ThirdPartyComponent has a custom implementation of shouldComponentUpdate, then you will have to find the specific prop which triggers update if it exists.
i'm rebuilding my portfolio with ReactJS as i'm learning this new language and i have 1 question. Should i use state or props only in a website where no content will need to be updated?
This is my main class:
class App extends Component {
state = {
name: 'My name',
job: 'Desenvolvedor Web'
}
render() {
return (
<div className="App">
<Header name={this.state.name} job={this.state.job}/>
</div>
);
}
}
And this is my Header.js
const Header = (props) => {
return(
<div className="Header">
<div className="conteudo text-center">
<img src="" className="rounded img-circle"/>
<h1>{props.name}</h1>
<h2>{props.job}</h2>
</div>
)
}
I guess my entire one page portfolio will follow this structure path, with not a big use of handles and changes in my DOM.
I'm sorry for this noob question, i'm really trying my best to learn React.
You should use both state and props in conjunction with one another. You're using both in your code perfectly fine. State is something that is managed by a component and can be passed down to a child via the props. A simple way of understanding this is that you can pass down the Parent component's state (App) to the child (Header) in the form of props which is an important concept in React.
State is both readable and writable whereas props are read only. Also, any change in the components state triggers a re-render.
Here, your state acts as the top/root level for the data that can be passed down to other components if it needs to be used again.
See these for more info.
What is the difference between state and props in React?
https://flaviocopes.com/react-state-vs-props/
State is for properties of your component that change and in turn cause your component to re-render. If you are only passing data down to read, props are a more appropriate choice.
I have a container containing some html with a <div id="ID"></div>. I have a react stateful component that I want to render in that div using
React.render(<ChildComponent data={this.props.data} />, document.getElementById('ID'))
When I call an action in childcomponent and udate the redux state, the props of the parent container do not update, only the ChildComponent re-renders with old values. Those props get updated when I refresh the page.
What is the solution to this ? Is there any other way to render React component in html so that the props can be updated with new props ?
Can you share your code for <ChildComponent> and its parent? There are a number of things you might be doing wrong but the thing that stands out is that it looks like you're rendering separately from its parent instead of as a child "prop" of its parent, like so:
<ParentComponent>
<ChildComponent />
</ParentComponent>
The official docs also have a lot of examples on how to get started: https://facebook.github.io/react/docs/hello-world.html
Hope this helps!